|Posted on 30 June, 2016 at 23:25|
The historical development of New Zealand’s foreign affairs is “the history of a colony becoming independent.”  When the British Parliament passed the New Zealand Constitution Act in 1852, New Zealand embarked on a journey of independence from Britain in exercising sovereignty – legislative, judicial, and executive authority – over its domestic affairs. However, ‘imperial interests’, (including foreign relations, external trade, the constitution and ‘native affairs’), were beyond the powers of the New Zealand Parliament. New Zealand did not obtain ‘Dominion status’ until 1907, but this also did not mean full sovereign independence because “the status of the dominions in international affairs is not necessarily identical with dominion status.” 
What does this all mean? Great question and when time pressure means we want quick answers we don't want to be reading through the bunkum to get to the crux of the matter. The writer above could have simply said that New Zealand has a foreign affairs service because we are our own country, making our own way in the world and need to be able to be part of the global community.
When you write, think about the reader you want to talk with. Have a conversation that they can easily understand.